Hardness testing instrument



p 3, 1938; H. IVIDIETERT 2,130,269

HARDNESS TESTING INSTRUMENT Filed Aug. 10, 1956 I? I7 26 6 28 A 29 I i 35 i y 20 .y 32 A will I8 33 Y I I r 30 |9 l4/ I 4O l I| I5 INVENTOR HARRY W- DIETERT B Y ATTORNEYS Patented Sept. Ed, "Edd 1 Claims.

This invention relates generally to instruments and refers more particularly to a hand instrument for determining the skin hardness of baked sand cores, bearing metals, stones used for grind- .3 ing purposes, and the like.

In the past, workmen in foundries have used their finger nails to scratch the baked cores to determine their skin hardness, and this, of course, has proven very unsatisfactory. Therefore, it

10 is an object of the present invention to provide an instrument that is capable of measuring automatically and accurately the depth of the scratch in thousandths of an inch to determine the skin hardness of the articles being tested.

15 Another object is to provide an instrument wherein a spring load'is applied to a diamond point to accomplish the results desired.

Another object is to provide a handy instrument that is self-contained and compact, and

m that may be readily manipulated.

ther objects, advantages and novel details of construction of this invention will be made more apparent as this description proceeds, especially when considered in connection with the accom- 5 panying drawing, wherein:

Figure l is a perspective View of an instrument embodying my invention;

Figure 2 is a bottom plan view thereof;

Figure 3 is a vertical sectional view through the instrument;

Figure 4 is a perspective view of the mechanism actuable by the tool for operating the pointer.

Referring now to the drawing, i is a casing having a removable base 2 provided with an opening it for a reciprocating work-engaging tpol l, and having a dial 5 at one side thereof over which a pointer 6 is movable to indicate the skin hardness of the material engaged by the tool. 40 Preferably this tool t has a diamond point i for engagement with the work and has a reduced shank B connected by a set screw 9 to the free end of a lever ill that is mounted at its other end upon a pivot ill within the casing. it is a plunger in line with the tool and actuable by the lever ill for translating motion to suitable mechanism within the casing -for actuating the pointer o. Preferably this plunger ll slidably engages vertically spaced bearing portions l2 and i3 rer spectively of the casing.

Referring now to the pointer actuating mechanism, Hi is a collar clamped on the plunger ii and engageable with the base It of a recess in the casing to limit downward movement of the plunger, while a removable plug H in the (or. ee s-12 bearing is is engageable by the upper end of the plunger to limit upward movement of the plunger.

i3 is a bracket fastened by a screw iii to a wall 28 of the casing and having offset arms 21 and 22 respectively, substantially parallel to said wall 5 29. Shafts 23 and 26 respectively are journaled in said arms and carry pinions 25 and 25. The shaft 23 also carries the pointer 6. As shown, pinion 26 meshes .With a rack 28 integral with the plunger ii, While the pinion 25 meshes with a gear 29 rigid with the shaft 2 3. Thus, sliding movement of the plungerv it causes pinion 26 to turn shaft 28, with the result that gear 29 on said shaft will cause pinion to turn shaft 23 carrying the pointer 6.

For controlling the downward force of the plunger ii, I have provided an adjustable angle bar 30 and a coil spring 3i. Preferably one Web of the angle bar has an elongated slot 33 therein receiving vertically spaced screws 34, while the 2d otherweb 35 of said bar has an elongated slot 36 therein receiving a laterally projecting pin 3? on the plunger ii. The coil spring 3! is terminally connected to the pin 3'? and to a pin lfi pro jecting laterally from the web 35 of the angle bar. 25

' Thus, adjustment of the bar 35] varies the tension of the spring 35 and hence the action of the plunger ii,

' In use the base 2 of the casing is placed flat against the surface to be tested and is then slid go over said surface so that the diamond point i will scratch the same. When this is done, the plunger il will move downwardly, depending upon the depth. of the scratch and, accordingly, will cause the pinion 26, gear 29 and pinion 25 to func- 5 tion sothat the depth of the scratch made by said point 'i, depending upon the skin hardness of the material being tested, will be recorded by the pointer ii on the dial. To accommodate grains of sand or other particles separated from 40 the specimen being tested by the diamond point 7 during the scratching operation, the base 2 has an elongated groove or channel-shaped recess 2 that extends lengthwise of the base from a point slightly in advance of the tool 3 to the 5 rear edge of the casing l.

In the present case suitable adjustments are provided for calibration so that a definite load on the tool i can be obtained. For example, during continued use, the point "i will wear. To compensate for this wear, the base 2 of the casing is pressed flat against a hard plane surface. Should pointer 6 fail to point to zero (0) on the dial 5, the latter is turned on the casing until pointer is at zero (0). The spring 38 applies 5 the load to plunger II and movement of the latter is controlled by the characteristics of the specimen being tested. The tension of spring 3| is adjusted by moving bar 30 until the load on the tool 4 is equal-to predetermined value. The collar I 4 is so placed on plunger II that it will cause point I to extend a predetermined distance from the base 2 of the casing. Thus, when my device is slid over the surface of the test specimen a predetermined loaded point 1 will scratch the said surface and the depth of such scratch is indicated on the dial 5 by the pointer 6 which is responsive to the action of the tool 4. The reading on the dial is taken as the measure of hardness of the specimen surface being tested.

What I claim as my invention is:

1. An instrument for measuring the skin hardness of articles, comprising a casing having a base for sliding engagement with the surface of an article to be tested, a predetermined loaded scratching element projecting through the base and operable when said base is slid over the article to scratch the surface thereof to be tested,

article to be tested, a dial upon one sideof the casing, and means movable over the dial and responsive to the action of the scratching element for indicating the depth to which the article is tested, said base having an opening therethrough,

a predetermined loaded scratching element pro jecting through the opening in the-base and operable when the base is slid over the surface to.

be tested to scratch the said surface, said scratching element being movable inwardly and outwardly automatically in the opening in the base as the latter is slid over the surface to be tested depending upon the skin hardness of said surface, and means carried by the casing responsive to the action of the scratching element for indicating the depth of scratch so made.

4. An instrument for measuring the skin hardness of articles, comprising a casing having a base for sliding engagement with the surface of an article to be tested, a predetermined loaded scratching element projected through the base and operable when said base is slid over the article to scratch the surface thereof to be tested, the base of. said casing being provided with a passageway for loose grains or particles separated from the article by the scratching element during the scratching action thereof, andmeans carried by the casing responsive to the action of the scratching element for indicating the depth 

